It is known in the art relating to reciprocating piston engines, such as internal combustion engines, to provide a piston having a head for absorbing combustion loads and a skirt for guiding the piston in a cylinder and absorbing side thrust loads. The piston head generally includes seal means, such as grooves for retaining piston rings for controlling blow-by of combustion gases and leakage of lubricating oil into an associated engine combustion chamber.
Both the piston rings and the piston skirt have outer surfaces that slide along the cylinder wall with lubrication to provide long life. However, the sliding surfaces cause a substantial portion of the friction losses normally occurring in an engine. Reduction of engine friction losses is a direct method of increasing engine efficiency and improving the mileage of automotive vehicles equipped with higher efficiency engines.